of the cia. the fbi had begun an investigation of the affair. >> patraeus calmed his unbehavior unacceptable for a cia director and he quit this afternoon. gary nurenberg is here on with what this all means. >> reporter: anita used the word legendary. patraeus wrote the book on how the cia conducted campaign. he changsd the wars in iraq and -- changed the wars in iraq and afghanistan. >> he was revered. >> he's described by many as the most influential and the most important general of his generation. >> reporter: that was his legacy until friday when it was revealed the fbi had begun an investigation of e-mails he exchanged with 39-year-old journalist paula broadwell, the author of a book about him. patraeus called his behavior unacceptable and said after being married for 37 years i showed extremely poor judgment by engaging in an extramarital affair. president obama accepted the -- he said he witches them the very best at this time. patraeus, a military phd changed the war in iraq and afghanistan. >> he's enormously important. >> reporter: usa military writer and author of the iraq book "